This invention relates to a method and apparatus for the automatic farming of softshell aquatic crustaceans, e.g., crabs and crayfish.
It is an established fact that crabs and crayfish in the "softshell" stage are an epicurean delight. The restaurant trade provides a steady demand for these softshell crustaceans and will pay a price per pound for them which can be 2 to 7 times the price which is paid for the same crustaceans in the "hardshell", i.e., intermolt/premolt, stage.
Crabs and crayfish both undergo a molt cycle which is repeated often when the crustaceans are immature and less often when they are mature. Harvesting of crabs and crayfish in the softshell stages requires that they be obtained from their environment, be it natural or artificial, as soon as undergoing a molt. Initially, after molt, the exoskeleton is very soft and the crab or crayfish is of prime commercial value. As time passes, the exoskeleton becomes leathery and then hard, the latter being the condition of the exoskeleton in the intermolt/premolt stage. Generally, in fed immature crabs and crayfish, the period between molts is about 60 days for the former and about 30 days for the latter.
Due to the relatively short time in which the exoskeleton of the crab or crayfish is suitable for the softshell trade, it has been suggested that these crustaceans be placed, while in the intermolt/premolt stage, into an artificial environment so that their molt can be carefully monitored. As soon (within 12 hours) as a molt has occurred, the subject crab or crayfish is harvested from the environment. Such harvesting may be accomplished by use of a dip net as is taught in U.S. Pat. No. 4,475,480. As can be appreciated, such harvesting is manpower-intensive and thus carries with it considerable expense.
Not only must the freshly molted crab or crayfish be soon removed from the environment for the purpose of obtaining the prime exoskeleton condition, but also, quick removal is necessary to prevent losses due to cannibalism. The molted crab or crayfish is a prime target for intermolts as the former's soft exoskeleton cannot provide a hard covering for protecting its vital organs or provide much functionality for its claws and legs. The problem of cannibalism is most aggravated in artificial environments as population densities are usually kept quite high for economic reasons. Thus, the commercial operator must go to great expense and provide continuous monitoring of the environment for new molts or must provide a means for protecting new molts from cannibalism.
The softshell crayfish industry has developed systems which encourage natural segregation of the molts and the intermolts/premolts. Exemplary of such systems is the one described in U.S. Pat. No. 4,475,480.
While such segregation systems help diminish losses from cannibalism, such systems do not mitigate the manpower and associated high costs which are required by manual harvesting.
It is therefore an object of this invention to provide a method and process for the automatic segregation and harvesting of molted aquatic crustaceans from a population of intermolts/premolts.